HBASE-29857 better handling NPE in BucketCache

[teamconfx]

This PR is for JIRA issue: https://issues.apache.org/jira/browse/HBASE-29857

The original JIRA issue is found in HBase v2.6.3, and fixed by HBASE-28839.
I tested with the same workload that I see the bug from v2.6.3 and verify the fix works in both master and branch-2.6.

However the current code still not handle NPE when persistence file is empty or corrupted explicitly.
This PR proposes a new checker to better catch the null from BucketCacheProtos.BucketCacheEntry.parseDelimitedFrom(in);.

[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 29s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
+1 💚	hbaseanti	0m 0s		Patch does not have any anti-patterns.
			_ master Compile Tests _
+1 💚	mvninstall	3m 21s		master passed
+1 💚	compile	3m 28s		master passed
+1 💚	checkstyle	1m 0s		master passed
+1 💚	spotbugs	1m 38s		master passed
+1 💚	spotless	0m 49s		branch has no errors when running spotless:check.
			_ Patch Compile Tests _
+1 💚	mvninstall	3m 1s		the patch passed
+1 💚	compile	3m 21s		the patch passed
+1 💚	javac	3m 21s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	1m 3s		the patch passed
+1 💚	spotbugs	1m 42s		the patch passed
+1 💚	hadoopcheck	11m 22s		Patch does not cause any errors with Hadoop 3.3.6 3.4.1.
+1 💚	spotless	0m 44s		patch has no errors when running spotless:check.
			_ Other Tests _
+1 💚	asflicense	0m 11s		The patch does not generate ASF License warnings.
		39m 34s

Subsystem	Report/Notes
Docker	ClientAPI=1.43 ServerAPI=1.43 base: https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-7685/1/artifact/yetus-general-check/output/Dockerfile
GITHUB PR	#7685
Optional Tests	dupname asflicense javac spotbugs checkstyle codespell detsecrets compile hadoopcheck hbaseanti spotless
uname	Linux f7f206766f5f 5.4.0-1103-aws #111~18.04.1-Ubuntu SMP Tue May 23 20:04:10 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 71d16e2
Default Java	Eclipse Adoptium-17.0.11+9
Max. process+thread count	84 (vs. ulimit of 30000)
modules	C: hbase-server U: hbase-server
Console output	https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-7685/1/console
versions	git=2.34.1 maven=3.9.8 spotbugs=4.7.3
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[Apache-HBase]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 12s		Docker mode activated.
-0 ⚠️	yetus	0m 2s		Unprocessed flag(s): --brief-report-file --spotbugs-strict-precheck --author-ignore-list --blanks-eol-ignore-file --blanks-tabs-ignore-file --quick-hadoopcheck
			_ Prechecks _
			_ master Compile Tests _
+1 💚	mvninstall	2m 41s		master passed
+1 💚	compile	0m 47s		master passed
+1 💚	javadoc	0m 23s		master passed
+1 💚	shadedjars	4m 25s		branch has no errors when building our shaded downstream artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	2m 18s		the patch passed
+1 💚	compile	0m 47s		the patch passed
+1 💚	javac	0m 47s		the patch passed
+1 💚	javadoc	0m 21s		the patch passed
+1 💚	shadedjars	4m 24s		patch has no errors when building our shaded downstream artifacts.
			_ Other Tests _
-1 ❌	unit	213m 13s	/patch-unit-hbase-server.txt	hbase-server in the patch failed.
		233m 36s

Subsystem	Report/Notes
Docker	ClientAPI=1.53 ServerAPI=1.53 base: https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-7685/1/artifact/yetus-jdk17-hadoop3-check/output/Dockerfile
GITHUB PR	#7685
Optional Tests	javac javadoc unit compile shadedjars
uname	Linux 7bdb232afab0 6.14.0-1018-aws #18~24.04.1-Ubuntu SMP Mon Nov 24 19:46:27 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 71d16e2
Default Java	Eclipse Adoptium-17.0.11+9
Test Results	https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-7685/1/testReport/
Max. process+thread count	5325 (vs. ulimit of 30000)
modules	C: hbase-server U: hbase-server
Console output	https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-7685/1/console
versions	git=2.34.1 maven=3.9.8
Powered by	Apache Yetus 0.15.0 https://yetus.apache.org

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